Collimated LED light field display

ABSTRACT

The present disclosure generally relates to light field displays and methods of displaying images with light field arrays. In one example, the present disclosure relates to pixel arrangements for use in light field displays. Each pixel includes a plurality of LEDs, such as micro LEDs, positioned adjacent respective micro-lenses of each pixel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/837,654, filed on Dec. 11, 2017, now U.S. patent Ser. No. 10,256,382,issued on Apr. 9, 2019, which claims benefit of U.S. Provisional PatentApplication Ser. No. 62/432,156, filed Dec. 9, 2016, both of which areherein incorporated by reference.

BACKGROUND Field

Embodiments of the present disclosure generally relate to a light fielddisplays and methods of displaying images with a light field array.

Description of the Related Art

Long held beliefs that our three dimensional (3D) perception of theworld around us is primarily related to stereoscopic vision (where theconvergence and/or divergence of two dimensional images viewedseparately by the left and right eye combine in the brain to give theperception of depth) have largely been proven untrue. We now know that,in addition to convergence/divergence, visual cues from head and eyemovements substantially influence a person's ability to perceive theworld about them in three dimensions. For example, if the viewer in FIG.1 moves her head from side to side she will perceive a relative motionbetween the bird and the mountain that is more than the relative motionshe perceives between the bird and the tree, thereby indicating themountain is the furthest away, which is generally known as motionparallax. Similarly, if she focuses her eye on the bird, the mountainwill appear to be more blurry than the tree, another indication of therelative distances of the tree and the mountain compared to the bird,which is generally known as blur cue interpretation. Both motionparallax and blur cue interpretation, as well as other visual cues,require angular information which includes both the intensity of lightrays reflected off a surface of an object and the angle of those lightrays with respect to a focal plane of the viewer as the light raystravel from the object to the viewer. Light rays of different angles,with respect to a focal plane of the viewer, reflected off the samesurface of an object will have different intensities. Advances in thearea of light field technology have provided light field cameras capableof capturing tremendous amounts of angular information, however, currentdisplay technologies are unable to capture and use all of the angularinformation captured by a light field camera for the display of theimage without user input.

Accordingly, what is needed in the art are high angular resolution lightfield displays.

SUMMARY

In one example, a pixel comprises a plurality of micro-lenses; and aplurality of collimated light emitting diodes (LEDs) positioned beneatheach micro-lens, wherein LEDs under a respective micro-lens of theplurality of micro-lenses are configured to generate light of the samecolor.

In another example, a light-field display comprises a plurality ofpixels, each pixel of the plurality of pixels comprising: a plurality ofmicro-lenses; and a plurality of collimated light emitting diodes (LEDs)positioned beneath each micro-lens, wherein LEDs under a respectivemicro-lens of the plurality of micro-lenses are configured to generatelight of the same color.

In another example, a light-field display comprises a plurality ofpixels, each pixel of the plurality of pixels comprising: a plurality oflight-directing features formed on a substrate panel; and a plurality ofcollimated light emitting diodes (LEDs) positioned beneath respectivelight-directing features, the plurality of collimated LEDs arranged inlinear strips according to a color of light generated thereby.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlyexemplary embodiments and are therefore not to be considered limiting ofscope, as the disclosure may admit to other equally effectiveembodiments.

FIG. 1 illustrates angular light information from the perspective of aviewer.

FIGS. 2A-2C schematically illustrate a pixel arrangement of a displayaccording to one aspect of the disclosure.

FIG. 2D schematically illustrates the directing of light rays from apixel arrangement, according to one aspect of the disclosure.

FIG. 3A is a schematic cross-sectional view of an LED, according to oneembodiment.

FIG. 3B is a sectional view of a portion of the LED described in FIG. 3Ataken along line 3B-3B of FIG. 3A.

FIG. 4 is a flow diagram illustrating a method of forming an LED,according to one embodiment.

FIGS. 5A-5H schematically illustrate formation of an LED according tothe method described in FIG. 4.

FIGS. 6A and 6B are schematic illustrations of pixel arrangements,according to other embodiments.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneembodiment may be beneficially incorporated in other embodiments withoutfurther recitation.

DETAILED DESCRIPTION

The present disclosure generally relates to light field displays andmethods of displaying images with light field arrays. In one example,the present disclosure relates to pixel arrangements for use in lightfield displays. Each pixel includes a plurality of LEDs, such as microLEDs, positioned adjacent respective micro-lenses of each pixel.

FIGS. 2A-2C schematically illustrate a pixel arrangement 202 of a lightfield display 200 according to one aspect of the disclosure. FIG. 2Aillustrates an enlarged partial view of a pixel arrangement 202 havingpixels 220 of a light field display 200. FIG. 2B schematicallyillustrates a plan view of a single pixel 220 of the pixel arrangement202. FIG. 2C schematically illustrates a plan view of a micro-lens andcollimated light emitting diodes (LEDs).

The light field display 200 is configured to produce a viewable image,and includes a plurality of pixels 220 controlled by a processor 204 togenerate light, thus forming the viewable image. The plurality of pixels220 is arranged in a pixel arrangement 202, such as a two dimensionalhexagonal array or other planar configuration. Each pixel 220 includes aplurality of micro-lenses 224 r, 224 b, 224 g, under which a pluralityof plurality of collimated (LEDs), such as collimated micro-LEDs, 226are positioned. In the example shown, the micro-lenses 224 r, 224 b, 224g of each pixel 220 are arranged in a triangular configuration withrespect to one another, which facilitates a dense configuration of thepixels 220 in the light field display 200. The plurality of pixels 220within the pixel arrangement 202 results in offset rows of micro-lenses(e.g., aligned in a horizontal direction but misaligned in a verticaldirection, or vice versa) in the pixel arrangement 202. This denseconfiguration improves perceived resolution by a viewer.

Beneath each micro-lenses 224 r, 224 b, 224 g is a plurality ofcollimated LEDs 226 (two are labeled in FIG. 2C) configured to emitlight of a desired wavelength. While only micro-lens 224 r is shown inFIG. 2C, it is to be understood that micro-lenses 224 b and 224 g aresimilarly configured. In one example, the LEDs 226 beneath themicro-lens 224 r are configured to emit red light, the LEDs 226 beneathmicro-lens 224 b are configured to emit green light, and the LEDs 226beneath micro-lens 224 b are configured to emit blue light. Statedotherwise, each group of LEDs 226 under a respective micro-lens 224 r,224 b, 224 g, is monochromatic. Typically, red LEDs 206 generate lighthaving a wavelength in the range between about 620 nm and about 780 nm,green LEDs 226 generate light having a wavelength in the range betweenabout 495 nm and about 580 nm, and blue LEDs 203 b generate light havingwavelengths in the range between about 450 nm and about 495 nm.

For purposes of this disclosure, each group of three or moremicro-lenses 224 r, 224 b, 224 g, and the LEDs 226 associated therewith,constitute a pixel 220, configured to emit RGB light. Each micro-lens224 r, 224 b, 224 g may be tailored to collimate and/or transmit lightof one color (or light within a specific wavelength range),corresponding to respective LEDs 226 disposed adjacent thereto. In oneexample, 24 LEDs 226 are positioned beneath each micro-lens 224 r, 224b, 224 g. In such an example, each pixel 220 is a single pixel ofspatial resolution that has a plurality of angular (e.g., directional)resolutions. Specifically, each angular resolution corresponds to one ofthe LEDs 226 under a single micro-lens, and thus, the 24 LEDs 226positioned beneath each micro-lens 224 r, 224 b, 224 g each correspondto one of 24 angular resolutions. Thus, the number of pixels 220, andspecifically the number of angular resolutions produced thereby,determine the effective resolution of the light field display 200.

In one example, the light field display 200 includes 1920×1080 pixels220. Each pixel 220 includes micro-lenses 224 r, 224 b, 224 g, eachhaving 24 LEDs 226 corresponding thereto. Thus, each pixel 220 has anangular resolution of 24, generating an effective light field resolutionof 46080×25920 for the light field display 200. It is contemplated thatmore or less than 24 LEDs 226 may be positioned beneath each micro-lens224 r, 224 b, 224 g, or that more or less than 1902×1080 pixels 220 maybe utilized in the light field display 200.

The LEDs 226 are positioned in a “stepped diamond” configuration beneatheach micro-lens 224 r, 224 b, 224 g. The “stepped diamond” configurationmaximizes the usable landscape under each micro-lens, furtherfacilitating densification of the light field display 200 and therebyimproving perceptible resolution. However, it is to be noted that otherarrangements of the LEDs 226 are also contemplated, such as hexagonal,rectangular, “cross-shaped” or “plus sign”. In one aspect, theconfiguration of LEDs 226 is selected to maximize the number of LEDs 226under a respective micro-lens.

The micro-lenses 224 r, 224 b, 224 g have a concave shape or surface fordirecting light from the LEDs 226 in a desired directions to provide adesired angular resolution. While the micro-lenses 224 r, 224 b, 224 gare described as being concave, it is contemplated that other lensshapes, such as convex lenses, flat lenses (e.g., meta lenses), orFresnel lenses, may be utilized. In one example, each LED 226 directslight upward, orthogonal to a plane of the pixel arrangement 202, e.g.,orthogonal to a plane of the pixels 220 and a plane of the LEDs 226. Theupward-directed light from each LED 226 is then directed in apredetermined direction by respective micro-lenses 224 r, 224 b, 224 g,as described with respect to FIG. 2D.

FIG. 2D illustrates the directional components of light exitingmicro-lenses 224 r, 224 b, 224 g of a pixel 220. To facilitateexplanation, only nine LEDs 226 are shown adjacent each micro-lens 224r, 224 b, 224 g (corresponding to an angular resolution of nine perpixel 220), however, it is to be appreciated that more or less than nineLEDs 226 may be utilized to generate a higher or lower angularresolution.

During operation, each LED 226 generates collimated light in a directionperpendicular to a surface of light field display 200, e.g., the z-axis.As the generated light passes through a respective micro-lens 224 r, 224b, 224 g, the light form each LED is directed in one of a plurality ofpredetermined directions, corresponding to angular resolutions of thepixel 220. The LEDs 226 of adjacent each micro-lens 224 r, 224 b, 224 gare configured to direct light (indicated by 212, two are marked) in adirection measured with respect to the deviation, here angle θ, of theprimary emission direction (the z-axis), and a directional componentbased on the North (N), east (E), south(S) and west (W) directions inthe plane of the display surface 210. Thus, the primary light emissiondirection of each LED can be notated as (direction, angle θ) forexplanation purposes, with the exception of a perpendicular(Z-direction) light ray, annotated as 0,0. Herein, the directionalcomponents N, S, E, and W respectively correspond to the upward,downward, rightward, and leftward directions of a display surface of thelight field display 200.

In one example, the LEDs 226 disposed equidistant from a central LED 226may each direct a light ray 212 which deviates from the Z direction byan angle θ (in a respective directional component). It is contemplated,however, that in some instances, angle θ may not be equal for each ofthe LEDs 226, depending on the desired angular resolution. Moreover, itis contemplated that additional LEDs 226 may be included, which directlight rays at an angle θ₁, different than angle θ, in order to provideadditional angular resolution. In such an example, the LEDs 226 havinglight directed at angle θ₁ may be positioned radially outward of theLEDs 226 having light directed at angle θ. In such an example, angle θ₁is greater than angle θ. It is to be noted that additional LEDs 226having light directed at angle θ₂, angle θ₃, and so forth, may befurther included, to increase angular resolution. As noted above, eachof the LEDs 226 generate light in a direction perpendicular to a displaysurface of the light field display 200, however, the particular angle θ(or angle θ₁, angle θ₂, etc.) is determined by the characteristics of arespective micro-lens 224 r, 224 b, 224 g.

In a specific example of the above embodiment, a first LED 226positioned centrally beneath a respective micro-lens 224 r, 224 b, 224 ghas light directed in the Z direction by a respective micro-lens 224 r,224 b, 224 g. A plurality of LEDs 226, spaced equidistant and radiallyoutward from the first LED 226, have light directed by a respectivemicro-lens 224 r, 224 b, 224 g at angle θ (in a corresponding compassdirection). A second plurality of LEDs 226, disposed outward of the LEDsof the first plurality of LEDs 226 and equidistant from the first LED226, have light directed by a respective micro-lens 224 r, 224 b, 224 gat angle θ₁ (in a corresponding compass direction). Additional LEDs 226,having lighted directed at additional angles θ_(i), may be furtherincluded to provide additional angular resolution.

Returning to FIG. 2D, to facilitate generation of an image, each LED 226under the micro-lens 224 r is operable with and corresponds to an LED226 at a corresponding location under micro-lens 224 b and micro-lens224 g. For example, the LED 226 under micro-lens 224 r which directs alight ray 212 toward (NW, θ) corresponds to the LEDs 226 undermicro-lens 224 b and micro-lens 224 g which also direct a light ray 212toward (NW, θ), thereby resulting in RGB light rays 212 for a particulardisplay angle of the angular resolution. Stated otherwise, each LED 226under one of the micro-lens 224 r, 224 b, 224 g, also has acorresponding LED 226 (of angular direction) under the remainingmicro-lenses of the pixel 220, in order to direct RGB light to aparticular angular location, facilitating display of an image.

While FIG. 2D is described with respect to compass directions, it is tobe noted that such directions are only used to facilitate explanation,and that angular directions are not limited to intervals of 90 degreesor 45 degrees from one another.

FIG. 3A is a schematic cross-sectional view of an LED 226 disposed on aportion of a display panel 310, according to one embodiment. FIG. 3B isa sectional view of a portion of the LED 226 described in FIG. 3A, takenalong line 3B-3B of FIG. 3A.

The LED 226 includes an active layer stack 304, a transparent conductiveoxide (TCO) layer 306 disposed on the active layer stack 304, anelectrically insulating layer 312, such as dielectric layer, disposed onthe active layer stack 304, and an electrically conductive reflectivelayer 316, such as a metal layer, disposed on the electricallyinsulating layer 312. Typically, the active layer stack 304 of the LED226 described herein is formed of one or more III-V materials, such asGaAs, GaN, InGaN, AlGaInP, or combinations thereof, and includes ap-type layer 304 a, an n-type layer 304 c, and one or more quantum well(QW) layers 304 b interposed between the p-type layer 304 a and then-type layer 304 c. In some embodiments, the blue and green LEDs 226 areformed using an active layer stack 304 that includes a InGaN layerinterposed between a p-type GaN layer and n-type GaN layer, where thewavelength of light emitted by the active layer stack 304, and thus thecolor of light provided by the LED 226, is determined by relativeconcentrations of indium and gallium in the InGaN layer. Alternatively,dopants, or color filter layers, may be used to provide the differentoutput colors of the LED 226. In some embodiments, red LED 226 areformed using an active layer stack 304 that includes an AlGaInP layerinterposed between a p-type GaP layer and an n-type GaAs layer.

The LED 226 is mounted to a display panel 310 of a light field display200 (shown in FIG. 2A), in a desired pixel arrangement 202 (shown inFIG. 2A), using a transparent conductive adhesive (TCA) layer 318disposed therebetween. When mounted, a major surface of the active layerstack 304 is substantially parallel to a plane of the display panel 310.Typically, the active layer stack 304 has a thickness T(1) between about10 nm and about 100 nm, such as about 30 nm and forms an ohmic contactwith the TCO layer 306 at the surfaces therebetween. The TCO layer 306is formed of a transparent conductive oxide material such as indium tinoxide (ITO) or doped conductive zinc-oxide, such as aluminum doped zincoxide (AZO) or gallium doped zinc oxide (GZO). The TCO layer 306 and atleast a portion of the active layer stack 304 form a circular orelliptical paraboloid shape, such as a substantially circular paraboloidshape at surfaces proximate to the electrically insulating layer 312.

The electrically insulating layer 312 is typically formed of atransparent dielectric material, such as silicon oxide, silicon nitride,or combinations thereof. The electrically insulating layer 312 isconformal to the circular paraboloid shape of surfaces of the TCO layer306 and at least portions of the surfaces of the active layer stack 304disposed therebeneath. In such a configuration, a reflective surface 316a of the reflective layer 316 disposed on the electrically insulatinglayer 312 forms an parabolic mirror, such as a circular or ellipticalparabolic mirror, having a focal point F at or proximate to a surface ofthe p-type layer 304 a. An opening 314 formed in the electricallyinsulating layer 312 enables a p-contact between the reflective layer316, disposed through the opening 314, and the TCO layer 306. In someembodiments, the TCA layer 318 provides an n-type contact to the activelayer stack 304. In other embodiments, the LED 226 is mounted to thedisplay panel 310 using a transparent non-conductive adhesive.

In some embodiments, the LED 226 further includes a sapphire layer (notshown) disposed between the active layer stack 304 and the display panel310, where the sapphire layer of the LED 226 is bonded to the displaypanel 310 using a non-electrically conductive transparent adhesive layer(not shown). In other embodiments, the LED 226 is mounted to a backpanel (not shown).

Typically, a surface of the active layer stack 304 proximate to the TCOlayer has a diameter D along the major axis thereof. In someembodiments, the diameter D is less than about 100 μm, such as less thanabout 50 μm, less than about 20 μm, less than about 10 μm, for exampleless than about 5 μm, or between about 0.1 μm and about 10 μm, such asbetween about 0.5 μm and about 10 μm, for example between about 0.5 μmand about 5 μm. In some embodiments, a ratio of the diameter D to aheight of the LED 226, herein height H, is more than about 0.2, such asmore than about 0.3, more than about 0.4, more than about 0.5, more thanabout 0.8, for example more than about 1.

In some embodiments, portions of the surface of the p-type layer 304 aare selectively treated, for example plasma treated, to desirably form anon-or-low-light transmission region 304 a(2) circumscribing a lighttransmission region 304 a(1). Plasma treating the surface of the p-typelayer in the non-or-low-light transmission region 304 a(2) desirablyincreases the resistance of the ohmic contact with the TCO layer 306disposed thereon to bound an area of effective light transmission fromthe active layer stack 304 to a light transmission region 304 a(1)centered about the focal point F. Bounding the area of lighttransmission to a region about the focal point F desirably increases thecollimation of light provided by the LED 226. The LED 226 generatescollimated light rays 212 in a direction that is substantiallyorthogonal (Z-direction) to the display surface 210 (e.g., X-Y plane).Thus, the axis of symmetry Z′ of the reflective surface 316 a is insubstantially the same direction as the Z-direction.

FIG. 4 is a flow diagram illustrating a method 400 of forming an LED226, according to one embodiment. FIGS. 5A-5H schematically illustrateformation of an LED according to the method described in FIG. 4.

The method 400 includes depositing a resist layer, such as the resistlayer 508 shown in FIG. 5B, on the surface of a substrate 500, atactivity 410. The substrate 500 includes a structural base 502, anactive layer stack 304 disposed on the structural base 502, and atransparent conductive oxide (TCO) layer 306 disposed on the activelayer stack 304. Typically, the structural base 502 is formed of alattice-matching material, such as sapphire or silicon carbide, and oneor more layers of the active layer stack 304 are epitaxially formedthereon. The resist layer 508 herein comprises a UV curable resinmaterial deposited and/or dispensed onto the surface of the substrate500. In some embodiments, the resist layer 508 is formed from aplurality of droplets of the UV curable resin material.

At activity 420, the method 400 further includes physically imprinting apattern into the resist layer 508 using an imprint lithography (IL)stamp 510. The imprint lithography (IL) stamp 510 includes one or moreparaboloid shaped openings 512 formed therein. Physically pressing theIL stamp 520 into the resist layer 508 displaces the resin materialabout the pattern of the IL stamp. The resin material is cured usingelectromagnetic radiation provided through the IL stamp to form apatterned resist layer 508 b comprising one or more paraboloid shapedfeatures. An axis of symmetry Z′ of the surface of the paraboloid shapedopenings 512 is parallel to a Z-direction and orthogonal to the X-Yplane. Typically, the IL stamp 510 is formed of a material that istransparent to the electromagnetic radiation 514, such as UV radiation,used to cure the resin material of the resist layer 508. In otherembodiments, the patterned resist layer 508 b is formed using a thermalimprint lithography process or a grey-scale lithography process. In someother embodiments, the IL stamp 510 and/or the patterned resist layer508 b is formed using a grey-scale lithography process. In some otherembodiments, the patterned resist layer 508 b is formed using acombination of grey-scale lithography and imprint lithography. It iscontemplated that other maskless direct lithography techniques may alsobe used.

At activity 430, the method 400 further includes transferring thepattern formed in the patterned resist layer 508 b to the TCO layer 306and the active layer stack 304 disposed therebeneath to form a patternedsubstrate, such as the patterned substrate 518 of FIG. 5F. In FIG. 5F,the patterned substrate 518 includes one or more paraboloid shapedfeatures 520 (three are shown). Typically, the pattern is transferredusing a dry etch process, such as an inductively coupled plasma (ICP)etch process or a reactive ion etching (RIE) process.

At activities 440, 450, 460 the method 400 further includes depositingan electrically insulating layer 312 onto the patterned substrate 518,forming one or more openings 314 in the electrically insulating layer312, and depositing a reflective layer 316 over the electricallyinsulating layer 312 to form one or more LEDs 226, such as the LED 226described in FIG. 3.

In some embodiments, the method 400 includes dicing the one or more LEDs226 along the dicing lines 522 shown in FIG. 5H. Dicing the one or moreLEDs 226 is typically done using laser scribing, mechanical sawing,water/solvent knifing, ion beam milling, a multi-layer photolithographyetch process, or a combination thereof. The LEDs 226 may be diced intoindividual LEDs 226, or groups of LEDs 226 in a predeterminedconfiguration, such as in a linear strip or the orientation shown inFIG. 2C. In some embodiments, the method 400 further includes removingall or a portion of the structural base 502 from the one or more LEDs226 before and/or after the dicing. In some embodiments, the structuralbase 502 is removed from the one or more LEDs 226 using a conventionallaser liftoff process, a chemical mechanical polishing (CMP) process, awet-etch process, or a combination thereof.

After formation of the LEDs 226, the LEDs 226 are positioned in apredetermined array or configuration adjacent a micro-lens, such asmicro-lens 224 r, 224 b, 224 g. In one example, LEDs 226 may be arrangedon and coupled to a display panel 310 (shown in FIG. 3A) in a pixelarrangement 202 (shown in FIG. 2A).

FIGS. 6A and 6B are schematic illustrations of pixel arrangements 602A,602B, according to other embodiments. The pixel arrangements 602A, 602Bmay be used in place of pixel arrangement 202 in FIG. 2A.

The pixel arrangement 602A includes a plurality of pixels 620A (only oneis shown for clarity). Each pixel 620A includes a plurality of red LEDs226 r _((1, 2, 3)), a plurality of green LEDs 226 g _((1, 2, 3)), and aplurality of blue LEDs 226 b _((1, 2, 3)), which generate light that issubsequently directed by a micro-lens array 624. The micro-lens array624 is a flat lens, such as a meta lens, that includes a plurality oflight-directing features 650 thereon (nine are shown, with onelight-directing feature 650 corresponding to a respective LED). Thelight directing-features 650 are positioned and configured to directlight from the red LEDs 226 r _((1, 2, 3)), the green LEDs 226 g_((1, 2, 3)), and the blue LEDs 226 b _((1, 2, 3)) in predetermineddirections, with corresponding LEDs having light directed in a sameangular direction. For example, LEDs 226 r ₁, 226 g ₁, and 226 b ₁ aredirected by the micro-lens array 624 in a same direction to generate afirst angular resolution (“View X”). Similarly, corresponding LEDS 226 r₂, 226 g ₂, and 226 b ₂, as well as corresponding LEDS 226 r ₃, 226 g ₃,and 226 b ₃ likewise are directed by the micro-lens array 624 togenerate additional angular resolutions (“View Y” And View Z”). It is tobe noted that additional LEDs 226 r _(i), 226 b _(i), 226 g _(i) may beincluded in each pixel 620A, and additional light-directing features 650may be included on the micro-lens array 624, to generate increasedangular resolution (e.g., more “views”). The light directing features650 may include or more of angled lenses, flat lenses, prisms, concavelenses, convex lenses, nano-fins such as titanium dioxide nano-fins, orother surface features configured to redirect light.

While only one pixel 620A is shown, the pixel arrangement 602A generallyincludes a plurality of pixels 620A_(i), arranged in array. Tofacilitate ease of manufacturing, LEDs 226 r _(i), 226 b _(i), 226 g_(i) of same color are manufactured on a single substrate in a densearray and then diced into linear strips 651 (or other configurations) onstructural bases 502. The linear strips 651 are then positioned in adesired configuration, for example, parallel and adjacent to oneanother, to form pixels for image generation. Similarly, light-directingfeatures 650 are formed on the micro-lens array 624 in a fully-densearray, corresponding to a desired pixel arrangement and angularresolution. In such a configuration, the number, placement, andorientation of the light-directing features 650 may be tailored todetermine light ray direction, the number of pixels (e.g., spatialresolution), and the number of angular views (e.g., angular resolution).For ease of manufacturing, the micro-lens array 624 includes anoptically-transparent substrate panel 670, such as a glass sheet, uponwhich the light-directing features 650 are formed. Formation of thelight-directing features 650 on the substrate panel 670 reducesmanufacturing time of a light-field display, because the light-directingfeatures 650 need not be individually aligned with a respective LED.Rather, proper positioning of the substrate panel 670 results inalignment of light-directing features 650 and all corresponding LEDS.

The example of FIG. 6A utilizes a single (unitary) micro-lens array 624(covering all pixels 620A_(i)), the micro-lens array 624 having aplurality of light-directing features 650 thereon. Alternatively, aplurality of discrete micro-lens arrays, for example, indicated by box655 (one is shown), may be used. In such an example, each discretemicro-lens array would include a plurality of light-directing features650.

While FIG. 6A illustrates micro-lens array 624 as a flat lens, it isalso contemplated that the micro-lens array 624 may include a pluralityof convex or concave lenses positioned over each pixel 620A, assimilarly shown with respect to FIG. 2B. In such an example, theplurality of convex or concave lenses may be formed on the substratepanel 670, or may be discrete units.

FIG. 6B illustrates a pixel arrangement 602B. The pixel arrangement 602Bis similar to the pixel arrangement 602A, but rather than linear strips651, the pixel arrangement 602B utilizes pixels 620B in clusters. In aspecific example, the clusters have a triangular arrangement, assimilarly shown and described with respect to FIG. 2C. Other clusterarrangements are contemplated. In addition to a densifying thearrangement of pixels per unit area, it is contemplated that thetriangular arrangement may improve perceived resolution which mayotherwise be reduced by the relatively large pixels, caused by theincreased number of LEDs per pixel.

While embodiments of the disclosure are discussed with respect to LEDs,it is contemplated that organic LEDS (OLEDs) may be used in placethereof. Additionally, it is to be understood that the angularresolution of a pixel by be adjusted by varying the number of LEDs permicro-lens of each pixel. For example, each micro-lens of a pixel mayinclude three or more corresponding LEDs, such as five or more, nine ormore, 16 or more, 25 or more, 36 or more, and the like.

Benefits of the disclosed subject matter include increased resolutioncompared to conventional displays.

While the foregoing is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

What is claimed is:
 1. A method of forming a light field display,comprising: forming a plurality of light emitting diodes from apatterned substrate, comprising: depositing a resist layer on a surfaceof a substrate, the substrate comprising: a structural base; an activelayer stack disposed on the structural base; and a transparentconductive oxide layer disposed on the active layer stack; patterningthe resist layer; and transferring the pattern formed in the resistlayer to the transparent conductive oxide layer and to at least aportion of the active layer stack disposed therebeneath to form thepatterned substrate; and arranging one or more of the plurality of lightemitting diodes beneath a light-directing feature of a plurality oflight-directing features formed on a substrate panel, wherein each ofthe light-directing features and at least one of the one or more lightemitting diodes positioned there beneath forms a pixel of angularresolution of the light field display.
 2. The method of claim 1, whereinthe active layer stack is formed of one or a combination of III-Vmaterials.
 3. The method of claim 1, wherein a surface of the activelayer stack which is proximate to the transparent conductive oxide layerhas a diameter less than about 100 μm.
 4. The method of claim 1, whereinpatterning the resist layer comprises one or a combination of an imprintlithography process or a grey-scale lithography process.
 5. The methodof claim 4, wherein patterning the resist layer comprises pressing animprint lithography stamp thereinto, the imprint lithography stampcomprising a plurality of paraboloid shaped openings formed in a surfacethereof.
 6. The method of claim 5, wherein the imprint lithography stampis transparent to electromagnetic radiation and patterning the resistlayer comprises exposing the resist layer to electromagnetic radiationthrough the imprint lithography stamp.
 7. The method of claim 6, furthercomprising depositing an electrically insulating layer over thepatterned substrate.
 8. The method of claim 7, further comprising:forming a plurality of openings in through respective portions of theelectrically insulating layer disposed over individual ones of theparaboloid shaped features; and depositing a reflective layer over theelectrically insulating layer.
 9. The method of claim 8, wherein theelectrically insulating layer is formed of a transparent dielectricmaterial.
 10. The method of claim 8, wherein a reflective surface of thereflective layer forms a substantially circular parabolic mirror. 11.The method of claim 1, wherein the active layer stack comprises a p-typelayer, an n-type layer, and one or more quantum well layers interposedbetween the p-type layer and the n-type layer.
 12. The method of claim1, further comprising dicing the light emitting diodes formed on thepatterned substrate into individual ones or groups before arranging oneor more of the plurality of light emitting diodes beneath alight-directing feature of the plurality of light-directing features.13. The method of claim 1, wherein the light field display comprises aplurality of pixels of spatial resolution each comprising a plurality ofthe pixels of angular resolution.
 14. The method of claim 13, wherein apixel of spatial resolution comprises light emitting diodes of differentcolors, and wherein groups of light emitting diodes that will emit thesame color of light are arranged in linear strips or clusters.
 15. Amethod of forming a light field display, comprising: forming a pluralityof light emitting diodes from a patterned substrate, comprising:depositing a resist layer on a surface of a substrate, the substratecomprising: a structural base; an active layer stack disposed on thestructural base; and a transparent conductive oxide layer disposed onthe active layer stack; patterning the resist layer to form a pluralityof paraboloid shaped features; transferring the pattern formed in theresist layer to the transparent conductive oxide layer and to at least aportion of the active layer stack disposed therebeneath to form thepatterned substrate; depositing an electrically insulating layer overthe patterned substrate; forming a plurality of openings in throughrespective portions of the electrically insulating layer disposed overindividual ones of the paraboloid shaped features; and depositing areflective layer over the electrically insulating layer; and arrangingone or more of the light emitting diodes beneath a light-directingfeature of a plurality of light directing features formed on a substratepanel, wherein each of the light-directing features and the one or morelight emitting diodes positioned there beneath forms a pixel of angularresolution of the light field display.
 16. The method of claim 15,wherein the active layer stack is formed of one or a combination ofIII-V materials, the electrically insulating layer is formed of atransparent dielectric material, and a surface of the active layer stackproximate to the transparent conductive oxide layer has a diameter lessthan about 100 μm.
 17. The method of claim 15, wherein patterning theresist layer comprises one or a combination of an imprint lithographyprocess or a grey-scale lithography process.
 18. The method of claim 15,wherein patterning the resist layer comprises pressing an imprintlithography stamp there into, the imprint lithography stamp comprising aplurality of paraboloid shaped openings formed in a surface thereof. 19.The method of claim 18, wherein the imprint lithography stamp istransparent to electromagnetic radiation and patterning the resist layercomprises exposing the resist layer to electromagnetic radiation throughthe imprint lithography stamp.
 20. A method of forming a light fielddisplay, comprising: arranging one or more of a plurality of lightemitting diodes beneath a light-directing feature of a plurality oflight directing features formed on a substrate panel, wherein each ofthe light-directing features and one or more of the light emittingdiodes positioned there beneath forms a pixel of angular resolution ofthe light field display, and wherein one or more of the plurality oflight emitting diodes comprises: an active layer stack; a transparentconductive oxide (TCO) layer disposed on the active layer stack, whereinthe transparent conductive oxide (TCO) layer and at least a portion ofthe active layer stack form a substantially circular paraboloid shape;an electrically insulating layer disposed on the transparent conductiveoxide (TCO) layer, the electrically insulating layer having an openingformed therein; and a reflective layer disposed on the electricallyinsulating layer, wherein the reflective layer comprises the reflectivesurface formed to collimate light emitted by the active layer stack andto direct the collimated light towards the light directing featurepositioned there above.